please help the problem (The best overloaded method match for 'System.Data.Common.DbDataReader.GetString(int)' has some invalid argument)
code
---------------
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
OleDbConnection conn = new OleDbConnection(conStr);
string str = ("select * from اساسي where الاسم الكامل='"+comboBox1.Text+"'");
OleDbCommand cmd = new OleDbCommand(str, conn);
OleDbDataReader myreader;
try
{
conn.Open();
myreader = cmd.ExecuteReader();
while (myreader.Read())
{
string sname = myreader.GetString("اسم الام");
textBox1.Text = sname;